The present invention relates generally to holographic data storage medium, and more particularly to accessing encrypted data files.
In holographic information storage, an entire page of information is stored at once as an optical interference pattern with a thick, photosensitive optical material. This is done by intersecting two coherent laser beams within the storage material. The first, called the data beam or signal beam, contains the information to be stored; the second, called the reference beam, is designed to be simple to reproduce—for example, a simple collimated beam with a planar wave front.
The resulting optical interference pattern of the two coherent laser beams causes chemical and/or physical changes in the photosensitive medium: a replica of the interference pattern is stored as a change in the absorption, refractive index, or thickness of the photosensitive medium. When the stored interference pattern is illuminated with one of the two waves that was used during recording, some of this incident light is diffracted by the stored interference pattern in such a fashion that the other wave is reconstructed. Illuminating the stored interference pattern with the reference wave reconstructs the data beam, and vice versa.